The present invention relates to methods of formulating dairy cow rations, and more specifically to a method of formulating rations based upon content of rumen-available protein and carbohydrate to provide optimized milk production and microbial synthesis.
U.S. Pat. No. 4,615,891, assigned to the assignee of the present inventors, describes a method of formulating dairy cow rations based on the content of non-structural carbohydrates and neutral detergent fiber in the total daily ration. The teachings of this patent have been employed with substantial benefit as reflected in increased milk production. For example, experimental results showed a milk yield on the order of 5.8% higher than in test herds fed previously conventional rations. The method included the steps of analytically determining the non-structural carbohydrate content of grain and forage components of daily rations, and adjusting the proportion and composition of at least one of the components to a level providing a total daily rations having about 30% to 45% non-structural carbohydrates. It is also preferred that the percentage of neutral detergent fiber of the ration components be determined, and that the results of non-structural carbohydrates to neutral detergent fiber be maintained at between about 0.9 and 1.20. The patent further considers the effects of rumen solubility of total protein in the ration, and recommends that the rumen soluble portion constitute between 15% and 25% of the total protein in the total daily ration. While the patent provides useful teachings based on specific recommended amounts or proportions of certain nutrients, it does not consider the effects of such time-related variables as digestion rates and periods of ruminal retention of protein and carbohydrates in the rations.
Microbial growth (in the rumen) is dependent upon simultaneous use of carbohydrates of energy and non-protein nitrogen (ammonia, amino acid and peptides) for protein synthesis. Without adequate energy, microbes will cease to grow and reproduce and ammonia will be lost from the rumen (urine). Likewise, if ammonia and amino acid are limiting, microbial growth will also cease, with a concomitant reduction in fiber digestion. The resultant outcome is not only an alteration in VFA proportion, (acetic-propionic) which significantly influences milk fat percent, but also decreased total energy availability to the cow. Thus, ruminal digestion is a dynamic process which involves nitrogen utilization as well as energy assimilation. Efforts to proportion protein to energy have been properly directed; however rumen availability data has not been adequately considered to these concepts.
The concept of rumen availability is both quantitative and qualitative. If considers those components which are not only solubilized, but also degraded, over time, in the rumen. Major nutrients which should be considered in evaluating rumen availability are protein and carbohydrates. Although rumen available protein does include the measurement of soluble protein, the two are not highly correlated. (Forages: r.sup.2 =0.05; ingredients: r.sup.2 =0.411) Rumen available carbohydrate and non-structural carbohydrate (NSC) are highly related to each other for most cereal type ingredients (r.sup.2 =0.70). However, for ingredient byproducts and forages, they are not well correlated (R.sup.2 =0.028); this is primarily associated with the rumen degradable fiberous components that are included in the rumen available carbohydrate value and not considered in NSC. For convenience, rumen available protein and rumen available carbohydrate will hereinafter be referred to as RAP and RAC, respectively.
Researchers have developed mathematical models and formulae that incorporate several components of ruminal digestion. This permits development and expression of RAP and RAC values as absolute numbers. However, to applicant's knowledge, specific RAP and RAC values or ranges which optimize milk yield and microbial synthesis have not previously been developed.
The principal object of the present invention is to provide a method of formulating a total daily ration for dairy cows based upon a properly adjusted combination of RAP and RAC to produce a positive response in lactation performance.
Another object is to provide a method of formulating dairy cow rations based upon RAP/RAC levels which maximized microbial protein synthesis and corresponds to increase in non-ammonia nitrogen flow.
Other objects will in part be obvious and in part appear hereinafter.